1. Field
The present disclosure relates to a driving support device for a vehicle, which is configured to control a trajectory of the vehicle.
2. Description of the Related Art
A driving support device configured to control a trajectory of a vehicle includes: a driving support control device configured to calculate a target steering angle for allowing a vehicle to travel along a target course; an electric power steering device configured to generate a steering assist torque; and an electric power steering control device configured to control the electric power steering device. The electric power steering control device is configured to calculate a target driving support torque for causing a steering angle to attain the target steering angle, and to control the electric power steering device so that a driving support torque attains the target driving support torque. Through control of the driving support torque, steering angles of steered wheels are controlled to attain target steering angles for allowing the vehicle to travel along the target course.
For example, in Japanese Patent Application Laid-open No. 2007-326447, there is described a driving support device configured to support steering of a vehicle so that the vehicle travels along a set target course, and to correct the target course when a steering operation input value input by a driver is a predetermined reference value or more. With this kind of driving support device, the driver can correct the target course to his or her intended course by performing a steering operation of the predetermined reference value or more that surpasses support steering by the driving support device.
In a driving support device, a target driving support torque for causing a steering angle to attain a target steering angle is calculated by an electric power steering control device, and an electric power steering device is controlled so that a driving support torque attains the target driving support torque. The driving support torque acts to urge steered wheels to cause its steering angles to attain target steering angles corresponding to the target steering angles so that a vehicle travels along a target course set, for example, as a center of a traveling lane.
Under the situation in which the steering angles of the steered wheels are controlled through control of the driving support torque so that the vehicle travels along the center of the traveling lane, the driver may try to cause the vehicle to travel along a path that is shifted leftward or rightward with respect to the center of the traveling lane without changing the target course targeted by the driving support. However, even when the driver steers the vehicle to satisfy his or her intention, the steering angles of the steered wheels are returned or maintained by the driving support torque to the steering angles in which the vehicle travels along the center of the traveling lane. As a result, the intention of the driver is not satisfied.
In the driving support device of the type described in Japanese Patent Application Laid-open No. 2007-326447, when the driver further steers the vehicle so that the vehicle travels in accordance with his or her intention, the magnitude of the steering operation becomes larger than a predetermined reference value, with the result that the target course itself is corrected. Further, the predetermined reference value of a steering operation for correcting the target course needs to be set to a large value in order to prevent the target course from being corrected unnecessarily. However, when the predetermined reference value is set to a large value, the magnitude of the steering operation becomes more unlikely to exceed the predetermined reference value. As a result, when the driver tries to change the traveling lane to, for example, a branch lane, the correction of the target course is delayed. Thus, even when the driver tries to change the traveling lane to, for example, a branch lane, the vehicle is maintained to travel along the target course.